The field of the invention is that of ordnance and warhead construction. The present invention relates to fragmentary warhead construction and to the construction of discrete fragment warheads. In particular, the invention relates to a novel way of constructing warhead fragments within a fragmenting rod, wherein a plurality of fragment kill mechanisms may be incorporated within a single rod.
In the prior art, most missile fragmentation warheads either use a solid steel case filled with explosive (which is the conventional design) or consist of explosive surrounded by a thin shell with "discrete" fragments glued to the shell which is generally called the discrete fragment design. In either case the warhead is then mounted into the ordnance section where structural loads are carried by a surrounding shroud.
An example of the conventional steel case design is LaRocca, U.S. Pat. No. 3,799,054 filed Mar. 26, 1974. This reference teaches a warhead for controlling the fragmentation of explosive devices having a cylindrical metallic fragmentation casing, wrapped with metallic strips of heavy density to cause fragments to form. This type of construction is limited to ordnance which has a single type of fragment, as the fragments are formed by the metal case. Because the fragmenting section is also load bearing and/or structurally supporting, some fragment materials are precluded. Only those materials which are structurally strong can be used for load bearing elements, thus eliminating many materials that could be used for fragments. In addition, the steel case design either employs heavy materials like LaRocca, or involves complex machining of the warhead case to form the fragments.
An example of discrete fragment design is represented by Brumfield et al., U.S. Pat. No. 3,977,327 filed Aug. 31, 1976. The Brumfield et al. reference is typical of many fragmentation schemes which precut fragments and then must sandwich them between steel or aluminum cylinders to form the case or missile airframe. Construction of this type of warhead is tedious and labor intensive.
It is also extremely difficult to manually place all the fragments in the required matrix pattern with each fragment aligned to precisely form the desired pattern. It is conventional to twist and shake the heavy warhead case to coax each fragment into its proprietary physical position, but gaps and spaces inexorably remain. These irregularities degrade performance and attenuate lethality.
It is, of course, possible to mix fragments of differing material when the discrete fragments are loaded into the warhead. A problem with this design is the uncertainty involved in the fragment pattern, as the fragments are dispersed radially from the center of the warhead upon detonation and the different type fragments will be on different bearings and heights. Thus, a small target might fall within a sector of the fragment pattern containing only one type of fragment. This would preclude any synergistic effect expected from mixing fragment kill mechanisms.
To date, most missile fragmentation warheads either use the conventional to discrete design. Both designs have associated advantages and disadvantages. In the conventional design the case is notched or welded to produce the desired fragment break up. The advantages to this design are that it reliably produces uniform size fragments with high velocities, and it is easily produced. One disadvantage to this design is that fragmentation customization is not easily performed. It is inherently difficult (if not possible) to use fragments of different materials without a performance penalty. Also, changing the fragment size and geometry is not easily done. In contrast, the discrete fragment design allows for easy tailoring of the fragments as fragments of differing materials and geometries are easily utilized, however, this warhead is much more costly to produce as each fragment must be attached to the warhead.
A related application by Applicants, filed even date with this application entitled Fragmenting Notched Warhead Rod, Ser. No. 07/740,524, addresses the production difficulties inherent with discrete fragment warheads. These notched rods are inserted as a unit into a warhead case to form the fragment matrix. The rod is notched so that when it is subjected to an explosive load it will break into individual fragments. The fragment size can be adjusted by varying the distances between notches, the thickness of the rod, and the rod width. Various materials can be selected to form this notched rod without concern for the strength of the warhead case. While these notched warhead rods greatly reduce the labor and cost associated with discrete fragmenting warhead construction, the fragment pattern uncertainty discussed above remains. The fragmenting rods may be laterally stacked on the periphery of the warhead with an amelioration of the fragment uncertainty problem, but complete kill mechanism integration throughout all fragment pattern sectors seems unlikely.
The present invention is an improvement of the fragmenting warhead rods designed to overcome the problems associated with fragment pattern uncertainty by formulating each rod with a plurality of fragment materials so that each rod will fragment into individual fragments having more than one kill mechanism. This insures that any target impacted, even by a single fragment, would suffer more than one kill mechanism.